Vent valve



FIG. 1 is a perspective view of a vent valve showing our new design, with the broken lines showing matter for illustrative purposes only and forming no part of the claimed design;

FIG. 2 is a front elevational view of the vent valve;

FIG. 3 is a rear elevational view of the vent valve;

FIG. 4 is a top plan view of the vent valve;

FIG. 5 is a right side elevational view of the vent valve;

FIG. 6 is a left side elevational view of the vent valve; and,

FIG. 7 is a bottom plan view of the vent valve. 

The ornamental design for a vent valve, as shown and described. 